CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 24,480	$ 32,545
Prepaid expenses and other current assets	1,111	1,493
Total current assets	25,591	34,038
Property and equipment, net	14	22
Operating lease right-of-use assets	631	734
Other assets	70	70
Total assets	26,306	34,864
Current liabilities:
Accounts payable	148	565
Accrued expenses	4,370	4,088
Operating lease liability	218	209
Total current liabilities	4,736	4,862
Operating lease liability, net of current portion	438	549
Total liabilities	5,174	5,411
Commitments and contingencies (Note 12)
Stockholders' equity:
Common stock, $0.001 par value, Authorized - 140,000 shares; Issued and outstanding - 52,999 and 52,818 at June 30, 2022 and December 31, 2021, respectively	53	53
Additional paid-in capital	766,025	764,861
Accumulated deficit	(744,946)	(735,461)
Total stockholders' equity	21,132	29,453
Total liabilities and stockholders' equity	26,306	34,864
Series A Preferred Stock [Member]
Stockholders' equity:
Preferred stock

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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- Definition

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).